The present invention relates to a feeding device for feeding single paper sheets from a stack, for example, in offset printing machines.
The purpose of the present invention is to provide a driving mechanism for the feeding device, of which the motion is controlled by sets of two cams within precise intervals, according to the need of a program of the operation, while all control mechanisms derive their operative motions separately in such manner that each mechanism is controlled by one set of two cams.
Feeding devices are known, in which the drive of the control mechanism for sheet moving suckers and the calliper is derived from cams in cooperation with resilient elements. (See for example U.S. Pat. Nos. 3,938,800 and 3,695,606).
The disadvantage of this feeding device consists in that, at higher printing speeds, the rollers of the control mechanisms do not follow the shape of the control cams, whereby inaccuracies in control operations result.
Another known feeding device (see for example Czechoslovakian Authorship Certificate No. 180,466) is arranged in such manner, that the motions of the controlled mechanisms are derived from one drum cam. The mechanism for controlling the sheet moving suckers is controlled by one bilateral cam path and a stationary, vertically mounted frame with a shaped groove. The mechanism of the sheet end hold-down calliper is controlled by a unilateral path of the drum cam and a resilient element.
The disadvantage of the last mentioned device consists in that the said drive is suitable for only simple universal suckers, which are intended for both lifting paper sheets and transporting them. This device cannot be used for separately operating sucker systems, wherein one sucker system lifts the papers sheets, and another sucker system feeds them into the printing machine.
A further disadvantage of such device consists in that the resilient elements for conrolling the calliper cause an inaccurate operation thereof.